Radio signal receiving system



Aug- 8 1939- s. M. RAsHl-:R 2,168,923

RADIO SIGNAL RECEIVING SYSTEI Filed Aug. l, 1933 2 Sheets-Sheet 1 ug- 8, 1939 s. M. BRASHER 2,168,923

RADIO SAIGNAL RECEIVING SYSTEM' L WWF/f7;

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UNITED STATES RADIO SIGNAL RECEIVING SYSTEM Samuel Murray Brasher, Decimal, Manitoba, Canada Application August 1, 1933, Serial No. 683,125 In Canada September 22, 1932 3 Claims.

My invention relates to improvements in wired or wireless telegraphy and telephony and resides in novel circuit arrangements for receiving and transmitting systems devoted to that art. In the accompanying diagrams my invention is shown as employed particularly for the reception of radio signals, and the objects of my invention are, rst, to provide a single capacity tuning unit controlling two, three or more tuned circuits lo thereby permitting of effective, sharp and easy tuning, together with increased amplification and clearness in respect to signals received; second, to provide a system in which the amplification is uniform at all frequencies; third, to provide a 1,5.A system which combines long and short wave reception or transmission in a single instrument and simple, easy and effective means of selecting the wave band desired.

With the above more important objects in 2,0,v View, the invention consists essentially in the arrangement and construction of parts hereinafter more particularly described, reference being had to the accompanying drawings in which:

Fig. 1 is a schematic diagram showing the basic 25V circuit employing my invention in which the primaries and secondaries of a plurality of radio frequency transformers are tuned in multiple, one condenser tuning all primaries and one condenser tuning all secondaries, and

3 0 Fig. 2 is a schematic diagram showing a circuit in which the secondaries only are tuned by a single condenser and in which is introduced a switching arrangement for the purpose of tuning the amplifier to a plurality of wave bands, and

3 5 Fig. 3 is a schematic diagram of an impedance coupled amplier in which the tuning is accomplished by the use of a single condenser controlling the several stages.

In the drawings like characters of reference 4g, indicate corresponding parts in the several iigures.

Referring to Fig. 1. The apparatus is provided with radio frequency transformers A, B, C and D, shown herein as three stages of radio fre- 45 quency amplification and detector stage, and vac- U num tubes E, F, G and H. The transformers each present primary and secondary windings 3 and 4 and the three element tubes shown have the usual control grid 5, plate or anode 6 and 5 QA filament or cathode 1.

` The primary coil 3 of transformer A is connected to an aerial and ground, or other input or collecting device, and one terminal of each transformer secondary 4 is connected to the con- 5, 5. trol grid 5 of the following tube. The other terminal of each transformer secondary 4, remote from the terminal connected to the control grid 5, is coupled through by-pass condenser 8 to the cathode l of the same tube. The plates 6 of tubes E, F and G are connected respectively 5 to one terminal of the primaries 3 of transformers B, C and D, and the plate E of tube H is connected to one terminal of an audio amplifier, or other output device, and the return connection from said amplifier, or device, is con- 10,

nected to the cathode of tube H. The terminals of the primaries 3 of transformers B, C and D, remote from the plate connections, are coupled respectively through by-pass condensers 9 to the cathodes of tubes E, F and G and connected to the plate current supply through choke coils N. The larnent leads for all tubes are connected through choke coils P to the plus and minus of the filament current supply, and the minus of the plate current supply and the plus of the grid biasing voltage are connected, as usual, to the minus of the filament supply. The minus of the grid biasing voltage is connected through choke coils T to the gridsof all tubes.

A variable or iixed condenser I supplied, has one side connected to the terminals of all transformer secondaries 4 approximately at the point where said terminals connect to by-pass condensers 8 and the other side thereof connected to the other terminals of said secondaries 4 ap- 30 proximately at the point where said other terminals connect to the grids of all tubes, there being loading coils S inserted in the latter connections. A second variable or fixed condenser 2 supplied, has one side connected to the ter- 35A minals of the primaries 3 of transformers B, C and D approximately at the point where these terminals connect to by-pass condensers 9 and to the corresponding terminal of primary 3 of transformer A approximately at the point where said corresponding terminal is connected to the said input or collecting device, and the other side of condenser 2 is connected to the other terminals of primaries 3 of transformers B, C and D approximately at the point where said other terminals are connected to the plates of tubes E, F and G and to the corresponding other terminal of the primary 3 of transformer A approximately at the point where said other terminal is connected to the corresponding other terminal of the aforesaid input or collecting device.

The circuit above described may be used as an amplifying circuit in a straight tuned radio frequency system and very 'good results may be obtained by tuning the primaries to a frequency V.

lower than the lowest frequency to be amplified and, with such an arrangement, the amplification tends to be more uniform due to the energy transfer being in inverse ratio to the frequency difference, thus tending to offset the variations in coil inductance due to variations in received frequency; or, in the case of both primaries and secondaries being tuned by variable condensers, the condensers may be operated by the same member and any desired frequency separation maintained.

The circuit is also suitable as an intermediate amplifier in systems such as the superhetero dyne.

Referring now to Fig. 2. 'I'his gure presents a circuit similar to that shown in Fig. 1, except that condenser 2 and its connections and loading coils S are omitted, and a switching arrangement is provided which permits the amplifier to be tuned over a plurality of wave bands. All circuit connections are the same as in Fig. 1 (excepting condenser 2 and its connections and loading coils S) except that, connected directly to the common conductor connecting the grids of all tubes with their several connections is one side of condenser I and to the other side of condenser I is connected one of the arms X of a bi-polar, multi circuit switch and to ve loi-polar points of said switch are connected loading coils II, I2,

I3, I4 and non-inductive conductor I5, and the other arm X of said bi-polar switch is connected to the common conductor connecting the terminals of transformer secondaries 4 which are remote from the terminals of said secondaries connected to the grids of all tubes.

The inductance of the coils II, I2, I3 and I4 vary with respect to each other so that, by connecting any one of said coils into the circuit by means of the switch, the overall inductance of the circuit is changed, and the amplier will respond to the wave band, or sequence of frequencies, over which the coils in conjunction with condenser I, will tune. With the switch set on the points to which conductor I5 is connected the amplifier will tune over the range of frequencies covered by the transformers in conjunction with condenser I.

Referring now to Fig. 3. This gure presents a circuit of the tuned impedance type and, while the method of transferring the signal from the plate of one tube to the grid of the next differs from that of the transformer coupled type of circuit, the employment of a single tuning condenser is equally feasible.

The input to the grid of the first tube may be an aerial and ground and transformer or other input or coupling device. The plates 6 of tubes E, F and G are coupled to the grids 5 of the following tubes through blocking condensers Ill. Connected between the grids of tubes F, G and H and their cathodes are non-inductive resistances R, and to the plates of tubes E, F and G are connected respectively one terminal of induction coils K, L and M, and the other terminals of these coils, remote from the plate connection, are connected respectively through choke coils N to the plate current supply and coupled by by-pass condensers 9 to the cathodes of the same tubes to the plates of which their opposite terminals are connected. The plate 6 of tube H is connected to one terminal of an audio amplier, or other output device, and the return con nection from said amplifier, or device, is connected tothe. cathode of said tube H.

A common conductor is connected to the plates 6 of tubes E, F and G approximately at the point where one terminal of coils K, L and M connect and another common conductor is connected to the other terminals of said coils K, L and M, remote from the terminals connected to the plates 6 of said tubes, approximately at the points where said other terminals connect to by-pass condensers 9 and between these two common con ductors is connected a condenser I for the purpose of tuning said coils K, L and M to a resonant period of such value as to offer the highest possible impedance to a selected frequency. The action of the circuit then is to impress upon the grids of tubes F, G and H with maximum intensity, the signal which it is desired to amplify.

The above descriptions of the several circuits will enable any one skilled in the art to construct an amplifier employing the invention and no special knowledge is required to operate the same. It is not thought necessary to go into the theory covering radio signalling as the principles are well understood. One of the outstanding features of an amplifier constructed in accordance with the design outlined above is its possession of what may be termed unisonant selectivity as opposed to the selectivity obtained by the filtering action of a number of tuned circuits. The circuit as a whole can be considered as a network resonant at the frequency to which it is tuned and its admittance to frequencies other than that to which it is tuned is very low.

While I have described and shown choke coils T, P, N in` the several circuits it is to be under stood that I do not desire to be limited to them as it is only necessary to have sufficient reactance, resistance or impedance in the several circuits to prevent feedback effects; and while in Fig. 2 I have shown and described a five point switch and four induction coils, the design is not necessarily limited to them as any desired number of coils and any suitable switch may be used. Nor do I desire to be limited to the exact manner in which, in the three specic arrangements shown, I have described my invention but aim to cover all that which comes within the spirit and scope of the appended claims.

Having described my invention what I claim as new and desire to secure by United States Letters Patent is:

1. In a radio frequency amplier including a plurality of amplifying vacuum tubes, each tube including anode, cathode and control grid, connected to and operating in conjunction with transformers, each transformer having primary and secondary windings, a single reactance connected on one side to the grids of all vacuum tubes and to the terminals of said secondary windings connected to said grids and on the other side to a single coil and through said single coil to the terminals of all secondary windings remote from the terminals connected to said grids.

2. In a radio frequency amplifier including a plurality of amplifying vacuum tubes, each tube including anode, cathode and control grid, connected to and operating in conjunction with transformers, each transformer having primary and secondary windings, a single reactance connected in parallel with the primaries of all transformers and tuning said primaries and a single reactance connected in parallel with the secondaries of all transformers and tuning said secondaries.

3. In a radio frequency amplifier including a plurality of amplifying vacuum tubes, each tube ondares and means for preventing feedback and intertube coupling, said means including impedances inserted between the several tube elements and their power, biasing or ground connections including connections to cathode other 5 than input and output returns.

SAMUEL MURRAY BRASHER. 

